Process for fabricating an electronic component incorporating an inductive microcomponent

ABSTRACT

The invention relates to a process for fabricating electronic components incorporating an inductive microcomponent placed on top of a substrate.  
     Such a component comprises:  
     a layer ( 10 ) of material having a low relative permittivity, lying on the top face of the substrate ( 1 );  
     a number of metal turns ( 30 - 31 ) defined on top of the layer ( 10 ) of material having a low relative permittivity; and  
     a copper-diffusion barrier layer ( 15 ) interposed between the metal turns ( 30 - 31 ) and the layer of material having a low relative permittivity.

TECHNICAL FIELD

[0001] The invention relates to the field of microelectronics. Morespecifically, it relates to a process for producing inductivemicrocomponents on a substrate, which itself can incorporate anintegrated circuit.

[0002] The components may especially be used in radiofrequencyapplications, for example in the field of telecommunications.

[0003] The subject of the invention is more specifically a process forobtaining circuits having a markedly higher performance than existingcomponents, especially as regards the value of the quality factor. Theprocess forming the subject of the invention also limits the number ofsteps needed to produce such components and ensures good reproducibilityof the characteristics of the components that it allows to befabricated.

PRIOR ART

[0004] In document FR 2 791 470, the applicant has described afabrication process for producing microinductors or microtransformers ontop of a substrate, and especially on top of an integrated circuit. Tosummarize, this process consists in depositing a layer of materialhaving a low relative permittivity and then etching this material at anaperture made in the hard mask, vertically above a pad for connectionwith the rest of the integrated circuit, so as to define aninterconnection hole, or via.

[0005] After having deposited a resist on top of the hard mask, saidresist is etched to form the channels defining the geometry of the turnsof the inductive component. Thereafter, copper is depositedelectrolytically on top of the connection pad and in the channelsdefined in the top resist.

[0006] Such a process has a number of drawbacks, among which may benoted essentially the fact that the electrodeposition step ensures boththe formation of the turns of the inductive component and the filling ofthe via, allowing contact with the metal pad connected to the integratedcircuit. Since these regions have different depths, it follows that theelectrodeposition is carried out differently at the turns and at thevia. Thus, certain irregularities are observed in the formation of theturns, these being prejudicial to good uniformity of the electricalperformance of the inductive component.

[0007] Furthermore, during the step of etching the top resist, it isnecessary to etch longer at the via, compared with the regions in whichthe channels intended to accommodate the turns are formed. Thisdifference in etch depth causes the release of chemical compounds at thebottom of the via, thereby interfering with the subsequent copperelectrodeposition operation.

[0008] One of the objectives of the invention is to alleviate thesevarious drawbacks, and especially to make it possible to producecomponents which have dimensional characteristics that are as precise aspossible, so as to give optimum electrical performance.

SUMMARY OF THE INVENTION

[0009] The invention therefore relates to a process for fabricating anelectronic component. Such a component incorporates an inductivemicrocomponent, such as an inductor or a transformer, which is placed ontop of a substrate and connected to this substrate by at least one metalpad.

[0010] In accordance with the invention, this process is one whichcomprises the following steps:

[0011] a) depositing a layer of material having a low relativepermittivity on the substrate;

[0012] b) depositing a layer forming a hard mask;

[0013] c) forming an aperture in the hard mask vertically above themetal pads;

[0014] d) etching the layer of material having a low relativepermittivity down to the metal pad, in order to form an interconnectionhole or via;

[0015] e) depositing a layer forming a copper diffusion barrier;

[0016] f) depositing a copper primer layer;

[0017] g) depositing a protective mask and removing it from the bottomof the via;

[0018] h) depositing copper, electrolytically, in the via;

[0019] i) removing the rest of the protective mask;

[0020] j) depositing a top resist layer with a thickness similar to thethickness of the turns of the inductive microcomponent;

[0021] k) etching the top resin layer in order to form channels definingthe geometry of the turns of the inductive microcomponent;

[0022] l) depositing copper electrolytically in the channels thusetched;

[0023] m) removing the rest of the top resist layer;

[0024] n) etching the copper primer layer between the copper turns; and

[0025] o) etching the copper-diffusion barrier layer between the turnsof the inductive microcomponent.

[0026] Thus, the process according to the invention links together anumber of steps which provide certain improvements over the processes ofthe prior art. It will be noted in particular that the copperelectrodeposition takes place in two separate steps, namely, to beginwith, a first step for filling the via, thereby allowing firstly copperto be grown up to level with the lower plane of the inductivemicrocomponent. In a second step, a copper electrodeposition process iscarried out, thereby forming simultaneously the turns of the inductivecomponent and the region of connection between the turns and the viaalready filled in during the prior deposition step.

[0027] Separating these two copper deposition steps in this way ensureshomogeneity of this deposition, this being favorable to uniformity ofthe shape of the turns, and therefore to the quality of the electricalperformance and the reproducibility of the process.

[0028] It will also be noted that this process can be used on varioustypes of substrate. Thus, in a first family of applications, the processcan be used on a semiconductor substrate and especially a substrate thathas been functionalized beforehand in order to form an integratedcircuit.

[0029] In other types of application, it may be a specific substrate,such as an amorphous substrate of the glass or quartz type, or moregenerally a substrate possessing electrical, optical or magneticproperties suitable for certain applications.

[0030] In practice, the material having a low relative permittivitywhich is deposited on the substrate, may be benzocyclobutene (BCB), orelse, a similar material whose relative permittivity is typically lessthan 3.

[0031] In practice, the thickness of this layer of material having a lowrelative permittivity may be between 10 and 40 microns, preferably beingabout 20 microns.

[0032] The thickness of this layer defines substantially the distancebetween the inductive component and the substrate. This distance,combined with the relative permittivity of the material of this layer,defines the parasitic capacitance existing between the inductivecomponent and the substrate, and it is highly desirable to minimize thiscapacitance.

[0033] In practice, the material used to form the hard mask on top ofthe BCB may be chosen from the group comprising: SiC, SiN, Si₃N₄, SiON,SiO₂, SiOC, Y₂O₃, Cr, taken individually or in combination.

[0034] The properties of these materials include good compatibility withBCB, especially good adhesion as hard mask on the BCB surface. Thesematerials have mechanical properties suitable for them to be used inmasking. This avoids the appearance of excessively high stresses at thejunction between the hard mask and the subjacent BCB layer. Moreover, bya judicious choice of these materials having the function of a hard maskfor the purposes of etching the vias, high selectivity of the BCBetching compared with these materials is acquired, so as to avoid anyunderetching of the BCB, and thus to obtain the desired profiles withoutdelamination.

[0035] This is because the stresses between the BCB and the hard maskcould be transferred right to the substrate and cause possible fracturesin the latter. Such phenomena owing to excessively high stresses areespecially observed in the processes of the prior art, which use thicklayers of certain metals to produce the hard mask on top of a BCB layer,with as consequence the risk of poor adhesion.

[0036] In practice, and especially when the hard mask is conducting, andtypically based on chromium, this hard mask may be removed before thecopper-diffusion barrier layer is deposited, so as to remove anyinter-turn conducting region.

[0037] According to another feature of the invention, a layer forming acopper diffusion barrier is deposited on top of the layer of materialhaving a low relative permittivity, when the hard mask has been removed.This barrier layer allows the subjacent layer to be isolated from thecopper that will be deposited subsequently, especially in the form ofthe primer layer. This characteristic barrier layer prevents themigration of copper through the layer of low relative permittivity,something which would have the effect of increasing this permittivity,and therefore of increasing the parasitic capacitance between theinductive microcomponent and the substrate, and of creating sources ofdefects. This barrier layer also prevents the copper from migrating intothe substrate, which would have prejudicial consequences on the qualityor the operation of the integrated circuit.

[0038] In practice, the barrier layer may be made of tungsten or from amaterial chosen from the group comprising: TiW, Ti, TiN, Ta, TaN, WN,Re, Cr, Os, Mo, Ru. These materials may be used individually or incombination.

[0039] Advantageously, in practice, the thickness of thecopper-diffusion barrier layer may be between 100 and 400 Å.

[0040] According to another feature of the invention, the process mayinclude a step of enriching the copper primer layer. This primer layeracts as the electrode for the subsequent copper electrodepositionoperations.

[0041] It may prove useful under certain conditions to improve theregularity and the morphology, the oxidation state of the copper, theroughness and the lack of nucleation sites in the primer layer. Thisprimer layer is deposited by a physico-chemical technique, moreparticularly by the technique called sputtering and its ionized metalplasma variant. In this case, a step to enrich this primer layer byexposing the primer layer to an electrolyte solution is carried out.This solution, containing copper salts, allows copper to be deposited inany spaces existing between the copper islands deposited beforehandduring the production of the primer layer, this enriching step thereforesmoothing out this primer layer so as to improve the subsequentelectro-deposition.

[0042] Advantageously, in practice, an annealing step may be carried outso as to increase the size of the copper crystals deposited during theelectrodeposition steps. This annealing step, typically carried out byexposing the component to a temperature between 150 and 400° C. for atime of a few minutes, ensures crystalline uniformity of the copperdeposited, and therefore the homogeneity and the conducting nature ofthe copper which will form the turns of the inductive component. Thus,the electrical properties of the component are improved by reducing thenumber of singularities that could be the source of resistive spots orpoints of mechanical weakness.

[0043] Advantageously, in practice, a step of decontaminating the copperliable to migrate into the substrate, especially at the lateral and rearfaces of the substrate, as well as around its circumference, may becarried out. This is because when the component is exposed to a solutioncontaining copper salts soluble in a judiciously chosen solvent, it isnecessary to remove any excess copper deposited. In fact, when thismetal is deposited using electrolytic techniques and with a specificcurrent distribution between the cathode and the anode, excess copper isgenerally observed to be deposited around the circumference of thesubstrate. Moreover, the convection and mass-transfer process, which isat the basis of the technique of depositing the element copper byelectrolysis, generates, on the lateral or rear faces of the substrate,a possible flux and diffusion over certain regions of the substrate. Toavoid any possible migration into the substrate, it is recommended touse this step.

[0044] In practice, this decontamination step may be performed afterboth of the two electrodeposition steps.

[0045] In practice, the protective mask deposited during the stepfollowing deposition of copper primer layers may be formed from anegative photoresist. This allows it to be easily removed at the bottomof the via in which the first copper electrodeposition will subsequentlytake place. Modifying the properties of the photoresist allows it tocure in the regions exposed during exposure of the lithography mask. Asurface deposition of copper is thus avoided, by virtue of the screenthus formed on the surface of the enriched primer layer by the curedresist.

[0046] Advantageously, in practice, before the step of depositing thetop resist, it is possible to carry out a treatment either withhexamethyldisilazane (HMDS) or divinyltetramethyldisilazane (DVTMDS), asdesired. This treatment makes it possible to obtain good copper-resistadhesion properties, thereby improving the growth of the copper on thevertical sidewalls of the channels intended to accommodate the turns.

[0047] According to other features of the invention, a number ofcleaning steps may be carried out using a chemical not corrosive tocopper. These cleaning steps may be carried out after the copperelectrodeposition, and after the step of depositing the copper primerlayer, or else after the copper-diffusion barrier layer has beendeposited.

[0048] The invention also relates to an electronic microcomponent thatcan be produced using the above-mentioned process. Such a componentincorporates an inductive microcomponent placed on a substrate andconnected to the latter by at least one metal pad.

[0049] This component comprises:

[0050] a layer of material having a low relative permittivity, lying onthe top face of the substrate;

[0051] a number of metal turns defined on top of the layer of materialhaving a low relative permittivity; and

[0052] a copper-diffusion barrier layer interposed between the metalturns and the layer of material having a low relative permittivity.

BRIEF DESCRIPTION OF THE FIGURES

[0053] The manner of implementing the invention and the advantages whichstem therefrom will become clearly apparent from the description of theillustrative example which follows, supported by the appended FIGS. 1 to19, which are sectional representations of a connection pad, of thesubstrate and of the various layers, that are deposited as the steps ofthe process proceed. The thicknesses of the various layers illustratedin the figures are given in order to allow the invention to beunderstood, but are not always in keeping with the actual thicknessesand dimensions.

MANNER OF IMPLEMENTING THE INVENTION

[0054] As already mentioned, the invention relates to a process forproducing inductive microcomponents on a substrate. In the exampleillustrated in the figures, the substrate (1) used is a substrate thathas been treated beforehand so as to form an integrated circuit.Nevertheless, other different substrates may be used, such as especiallysubstrates based on quartz or glass.

[0055] Thus, such a substrate (1), as illustrated in FIG. 1, includesthe top level (2) of the actual integrated circuit, surmounted by alayer (3) of doped substrate.

[0056] In the figure shown the substrate (1) also includes a metal pad(4), made of a metal which may be aluminum or an aluminum alloy orcopper, the top face (5) of which is accessible. The edges (6) of thismetal pad and the top face (7) of the doped layer are covered with apassivation layer (8).

[0057] The process according to the invention may link together thevarious steps described below, it being understood that some of them maybe carried out differently, while still obtaining similar results. Someof the steps may also be regarded as useful, but not absolutelyessential, and therefore in this regard may be omitted without departingfrom the scope of the invention.

[0058] Step 1

[0059] The first step consists in cleaning the top face (5) of the metalconnection pad (4) and of the passivation layer (8) deposited on thesubstrate. This cleaning operation is carried out by a wet chemicaltechnique.

[0060] Step 2

[0061] As illustrated in FIG. 2, the process continues with thedeposition of a layer (10) of benzocyclobutene (BCB), or of anyequivalent material possessing a relative permittivity of less than 3.This deposition is carried out by a process called spin-on deposition.The thickness deposited is about 20 microns.

[0062] Step 3

[0063] The process continues with a step of cleaning the top face (11)of the BCB layer (10). This cleaning, carried out with a suitablesolution ensures that the top face (11) of the BCB layer (10) is cleanedand prepared.

[0064] Step 4

[0065] As illustrated in FIG. 3, the process continues with thedeposition of a layer (12) forming a hard mask on top of the BCB layer(10). This layer (12) has a thickness of around 200 Å. The materialemployed is preferably silicon carbide (SiC), but it could also be SiOC,SiN, Si₃N₄, SiON, SiO₄, SiO₂, Cr or Y₂O₃ or any other material, as longas the etching selectivity with respect to the material of the bottomlayer is at least 10:1. This hard mask layer (12) may be deposited by aplasma-enhanced chemical vapor deposition (PECVD) process.

[0066] Step 5

[0067] Thereafter, an aperture (13) is made in the hard mask (12) asillustrated in FIG. 4, by a lithography process and suitable chemicaletching using a wet process, such as a solution based on hypophosphoricacid at a temperature of 180° C. if the hard mask is composed of siliconnitride, or dry plasma etching using a reactive gas containing fluorine,such as CF₄/H₂, for example.

[0068] Step 6

[0069] The process then continues as illustrated in FIG. 5 with theetching of the BCB layer (10), vertically above the metal connection pad(4), so as to form the via (14). The BCB layer may be etched especiallyby using a gas mixture such as the Ar/CF₄/O₂ mixture, or else by aradiofrequency plasma using other reactants.

[0070] Step 7

[0071] The process continues, as illustrated in FIG. 6, with the removalof the hard mask which remained on the remaining parts of the BCB layer(10). This hard mask is removed by etching, by using a solution composedof Ce (SO₄)₂/2(NH₄)₂SO₄/HClO₄/deionized water if the hard mask is madeof chromium for example. The hard mask may also not be removed, andtherefore kept on the BCB layer (10), depending on the material fromwhich it is made, and especially if it is made of SiC, SiN, or SiON, forexample.

[0072] Step 8

[0073] The via (14) may then be cleaned using various methods. Thus, itmay be cleaned chemically, employing a non-corrosive semi-aqueousmixture. It may also be cleaned by a dry method, using an argon plasmawith a power of around 300 kilowatts, by subjecting the region (14) toradiofrequency waves for a time of about one minute, at roomtemperature.

[0074] Step 9

[0075] As illustrated in FIG. 7, the process continues with thedeposition of a copper-diffusion barrier layer (15). This layer (15) ispreferably made of a titanium-tungsten alloy or else is a superpositionof titanium and titanium nitride, or else of tantalum and tantalumnitride. This layer (15) may also be made of tungsten nitride, or elseby a single layer of tungsten, molybdenum, osmium or ruthenium. Thislayer (15), having thickness of between 100 and 400 Å, may be depositedby various techniques, and especially by sputtering, a process alsoknown as IMP-PVD (Ionized Metal Plasma-Physical Vapor Deposition), or byCVD (Chemical Vapor Deposition) or ALD (Atomic Layer Deposition)techniques.

[0076] Step 10

[0077] As illustrated in FIG. 8, the process continues with thedeposition of a copper primer layer (16). This primer layer (16) may bedeposited by various techniques, and especially by sputtering, a processalso known as IMP-PVD (Ionized Metal Plasma-Physical Vapor Deposition)or by CVD (Chemical Vapor Deposition) or ALD (Atomic Layer Deposition)techniques. The layer thus obtained has a thickness typically of between500 and 2000 Å.

[0078] Step 11

[0079] The process continues, as illustrated in FIG. 9, with a step ofenriching the primer layer (16) electrolytically. A solution of coppersalts such as CuSO₄.5H₂O, may be used. A reducing agent, such asdimethylamineborane may also be provided, as substitution of theelectrolytic current.

[0080] This enrichment step makes it possible to fill the spaces betweenthe copper islands that were deposited beforehand in order to form theprimer layer. The surface of the primer layer (16) is thus smoothed,thereby favoring the subsequent electrodeposition step. This step allowsthe thickness of the primer layer inside the via, and more particularlyon the inner faces and at the bottom of the via, to be increased.

[0081] Step 12

[0082] Thereafter, as illustrated in FIG. 10, a layer (18) of negativephotoresist is deposited on those faces (17) of the primer layer (16)which are parallel to the substrate. This deposition (20) has also takenplace at the bottom (19) of the via, but not on the vertical walls (21)of said via. This layer (18, 20) of negative photoresist has a thicknessof around 5000 Å.

[0083] Step 13

[0084] The process continues, as illustrated in FIG. 11, with theremoval of the layer (20) of negative photoresist placed at the bottom(17) of the via (14). The remainder (18) of the negative photoresist isnot removed following the photoexposure process, which cures the exposedresist.

[0085] Step 14

[0086] The process continues with a cleaning step by applying a solutionthat does not corrode copper, so as to obtain an optimum surface finishas regards the bottom (19) of the via and its sidewalls (21). Thesolution used is an aqueous solution which may contain molecules of acorrosion inhibitor, such as benzotriazole.

[0087] Step 15

[0088] As illustrated in FIG. 12, the process continues with copperelectrodepositions so as to fill (22) the via (14) using a techniqueknown as “electroplating”. This technique is based on the use of anelectrolyte solution the formulation of which is judiciously defined inorder to obtain optimum copper quality, namely a resistivity beforegrain growth during annealing of between 1.9 μΩ.cm and 2.3 μΩ.cm, andpreferably between 2 μΩ.cm and 2.15 μΩ.cm. Moreover, the definition ofthe deposited layer depends directly on the geometry of theelectrochemical cell, on the distance between the cathode and the anode,on the shape and characteristics of each electrode, and on the regionand the surface on which it will be deposited. The solutions used may,for example, be those sold under the name “Cu VIAFORM” by Enthone or “CuGLEAM ELECTRODEPOSIT 6000” by Shipley.

[0089] Step 16

[0090] Thereafter, a decontamination step may be carried out, making itpossible to remove any trace of copper which would be liable to migrateinto the substrate or into any other part in which copper ions coulddeposit themselves. This decontamination step makes it possible inparticular to clean the rear of the substrate and the peripheral regionsof the substrate. The expression “peripheral regions” includes thelateral faces of the substrate, perpendicular to the principal plane ofthe substrate, and the edges of the substrate on which excess depositsof copper associated with the copper deposition process, depending onthe technique used, may have accumulated.

[0091] This decontamination step is carried out by a wet chemicaltechnique by means of a tool allowing the substrate to be treated faceby face, using a solution containing a mixture of hydrogen peroxide andsulfuric acid.

[0092] Step 17

[0093] The process then continues as illustrated in FIG. 13 with theremoval, by etching, of the negative photoresist mask which protectedthe copper primer layer on top of the BCB regions (10).

[0094] Step 18

[0095] The process continues with a cleaning step by applying a solutionthat does not corrode copper, so as to remove any trace of resist on theprimer layer (10) for the purpose of making it easier to deposit thesubsequent layers.

[0096] Step 19

[0097] The process continues with what is called an “annealing” step,allowing the crystalline structure of the copper (22) deposited in thevia (14) to be reorganized by increasing the size of the elementarycrystalline grains. This step uses a technique known as RTP (RapidThermal Processing) during which the component is subjected to atemperature of around 150 to 400° C., preferably 300° C., for a time of10 seconds to 30 minutes and preferably for 5 minutes. The component ismaintained in an atmosphere of an inert gas or in a vacuum, preventingany oxidation and diffusion of oxygen into the crystalline medium of thecopper. The parameters are judiciously defined in order to obtain theoptimum copper quality, namely a resistivity after grain growth ofbetween 1.7 μΩ.cm and 2 μΩ.cm, but preferably between 1.72 μΩ.cm and1.82 μΩ.cm.

[0098] Step 20

[0099] The process then continues with hexamethyldisilazane (HMDS) ordivinyltetramethyldisilazane (DVTMDS) being spread by a centrifugalforce. This step makes it possible to optimize the surface finish of thevertical sidewalls of the resist which will be subsequently deposited,and into which resist HMDS or DVTMDS will be able to diffuse during theannealing steps, since these additives lower the surface tension of thisresist. Such a treatment promotes better adhesion of copper to thevertical sidewalls of the resist deposited subsequently, which form thewalls of the via (14).

[0100] Step 21

[0101] The process continues with the deposition of a top layer (25) ofresist, as illustrated in FIG. 14. This resist (25) is of the positivephotoresist type, for allowing the subsequent lithographic operations.This resist (25) is resistant to the acid chemistry of theelectrodeposition.

[0102] The top layer (25) of resist thus deposited has a thickness ofbetween 10 and 50 microns, preferably between 20 and 40 microns,depending on the height of the turns of the inductive component.

[0103] Step 22

[0104] The process continues, as illustrated in FIG. 15, with theetching of this top layer (25) of resist in order to define, between theremaining regions (27), channels (28, 29) which will subsequentlyreceive the copper that will form the turns of the inductive component.This etching operation is carried out by a standard lithography process.

[0105] Step 23

[0106] The process continues, as illustrated in FIG. 16, with anelectrodeposition of copper on top of the primer layer (16). It will benoted that the thickness deposited in the peripheral channels (28) isthe same as that in the channel (29) lying vertically above the via (4)so that the growth is substantially similar. In this case, the copperelectrodeposition may be specifically carried out by means of anelectrochemical deposition tool using a consumable copper anode and achemical solution chosen from the various producers, such as thesolution “Cu GLEAM ELECTRODEPOSIT 6000” sold by Shipley. The copperdeposited typically fills between 70% and 90% of the channels (29) so asto give copper thicknesses for the turns of greater than 10 microns.

[0107] Step 24

[0108] The process continues with a decontamination step identical tothat described in step 16.

[0109] Step 25

[0110] The process continues with the removal of the top resist regions(27) which defined the various channels (28, 29). Removal of this resist(27) clears the space (32) between the turns (30-31) so as to limit theinter-turn capacitance. This removal also makes the metal layers (16,15) lying between the turns (30-31) accessible, so that they can beremoved subsequently.

[0111] Step 26

[0112] The process continues, as already mentioned in step 18, with acleaning step by applying a solution that does not corrode copper so asto remove all the residues left by the lithography step, the chemicalprocess of which may use a compound consisting of amines and ofmolecules that do not corrode copper, chosen from the manufacturers ofsuch products, such as the product ACT-970 from Ashland.

[0113] Step 27

[0114] The process continues, as illustrated in FIG. 18, with wetanisotropic etching of the copper primer layer (16), for example bymeans of a sulfuric acid solution or a nitric acid solution thatincludes benzotriazole.

[0115] Step 28

[0116] The process continues, as illustrated in FIG. 19, with theetching of the copper-diffusion barrier layer (15) which depends on thechoice of material for the copper diffusion barrier. As an example, whenthe diffusion barrier layer is a superposition of two layers—a titaniumlayer and a titanium nitride layer—this diffusion barrier may be etchedby an aqueous solution composed of ethylenediaminetetraacetic acid(EDTA) and of hydrogen peroxide in a ratio of 2 to 1, at a temperatureof between 45° C. and 90° C., and preferably about 65° C. However, thisexample is not limiting and other chemical solutions according to theprior art may be used.

[0117] This means that the various turns (30) and the central part (31)of the inductive microcomponent are therefore electrically independent.

[0118] Step 29

[0119] The process continues with an annealing step similar to thatdescribed in step 19.

[0120] Step 30

[0121] The process continues with a cleaning step using a solution thatdoes not corrode copper, such as one similar to that described in steps18 and 26.

[0122] It is apparent from the foregoing that the process according tothe invention makes it possible to obtain inductive microcomponentswhich have a very high quality factor, because of a controlled distancebetween the substrate and the principal plane of the inductivemicrocomponent. Typically, the quality factors obtained are greater than40 at frequencies of around 2 gigahertz.

[0123] Splitting the copper electrodeposition into two separate stepsmakes it possible to optimize the regularity of the shape of the variousturns without increasing the manufacturing costs, and therefore ensuresgood reproducibility of the process resulting in the production of amicrocomponent having electrical properties very similar to thosedefined at the design stage and therefore the expected electricalperformance.

[0124] Moreover, the advantage of this present invention is that itcontrols the interfaces between the various layers of materialsdeposited and formed, with the consequence that the performance of thedevice is significantly improved and sources of defects are considerablyreduced.

1. A process for fabricating an electronic component, incorporating aninductive microcomponent placed on top of a substrate and connected tothe latter via at least one metal pad, which comprises the followingsteps, consisting successively in: a) depositing a layer of materialhaving a low relative permittivity on the substrate; b) depositing alayer forming a hard mask; c) forming an aperture in the hard maskvertically above the metal pads; d) etching the layer of material havinga low relative permittivity down to the metal pad, in order to form aninterconnection hole or via; e) depositing a layer forming a copperbarrier diffusion; f) depositing a copper primer layer; g) depositing aprotective mask and removing it from the bottom of the via; h)depositing copper, electrolytically, in the via; i) removing the rest ofthe protective mask; j) depositing a top resist layer with a thicknesssimilar to the thickness of the turns of the inductive microcomponent;k) etching the resist layer in order to form channels defining thegeometry of the turns of the inductive microcomponent; l) depositingcopper electrolytically in the channels thus etched; m) removing therest of the top resist layer; n) etching the copper primer layer betweenthe copper turns; and o) etching the copper-diffusion barrier layerbetween the turns of the inductive microcomponent.
 2. The process asclaimed in claim 1, wherein the substrate is a semiconductor substrateforming an integrated circuit.
 3. The process as claimed in claim 1,wherein the substrate is an amorphous substrate of the glass or quartztype.
 4. The process as claimed in claim 1, wherein the material havinga low relative permittivity deposited on the substrate isbenzocyclobutene.
 5. The process as claimed in claim 1, wherein thethickness of the layer of material having a low relative permittivity isbetween 10 and 40 microns, preferably about 20 microns.
 6. The processas claimed in claim 1, wherein the material used for the layer formingthe hard mask is chosen from the group comprising: SiC, SiN, Si₃N₄,SiON, SiO₂, SiOC, Y₂O₃, Cr, taken individually or in combination.
 7. Theprocess as claimed in claim 1, wherein the hard mask is made ofchromium, which also includes a step of removing the hard mask beforethe layer forming the copper diffusion barrier is deposited.
 8. Theprocess as claimed in claim 1, wherein the material used for thecopper-diffusion barrier layer is chosen from the group comprising: TiW,Ti, TiN, Ta, TaN, W, WN, Re, Cr, Os, Mo, Ru taken individually or incombination.
 9. The process as claimed in claim 1, wherein the thicknessof the copper-diffusion barrier layer is between 100 and 400 Å.
 10. Theprocess as claimed in claim 1, which includes a step of enriching thecopper primer layer.
 11. The process as claimed in claim 1, whichincludes an annealing step intended to increase the size of the coppercrystals deposited during the electrodeposition steps.
 12. The processas claimed in claim 1, which includes a step of decontaminating thecopper liable to migrate into the substrate, especially at the lateralfaces of the substrate.
 13. The process as claimed in claim 12, whereinthe decontamination step takes place after at least one of the copperelectrodeposition steps.
 14. The process as claimed in claim 1, whereinthe protective mask deposited during the step following deposition ofthe copper primer layer is formed from a negative photoresist.
 15. Theprocess as claimed in claim 1, wherein, before the step of depositingthe top resist layer, a treatment with hexamethyldisilazane (HMDS) ordivinyltetramethyldisilazane (DVTMDS) is carried out, this treatmentbeing intended to give said top resist good copper adhesion properties.16. The process as claimed in claim 1, which includes at least onechemical cleaning step not corrosive to copper after the copperelectrodepositions and/or after the steps of depositing the copperprimer layer and/or of the copper-diffusion barrier layer.
 17. Theprocess as claimed in claim 1, wherein the copper deposition intended toform the turns is carried out in order to give a copper thickness ofgreater than 10 microns.
 18. An electronic component, incorporating aninductive microcomponent placed on top of a substrate and connected tothe latter via at least one metal pad, which comprises: a layer ofmaterial having a low relative permittivity, lying on the top face ofthe substrate; a number of metal turns defined on top of the layer ofmaterial having a low relative permittivity; and a copper-diffusionbarrier layer interposed between the metal turns and the layer ofmaterial having a low relative permittivity.
 19. The component asclaimed in claim 18, wherein the substrate is a semiconductor substrateforming an integrated circuit.
 20. The component as claimed in claim 18,wherein the substrate is an amorphous substrate of the glass or quartztype.
 21. The component as claimed in claim 18, wherein the materialhaving a low relative permittivity deposited on the substrate isbenzocyclobutene.
 22. The component as claimed in claim 21, wherein thethickness of the layer of material having a low relative permittivity isbetween 10 and 40 microns, preferably about 20 microns.
 23. Thecomponent as claimed in claim 18, wherein the material used for thecopper-diffusion barrier layer is chosen from the group comprising: TiW,Ti, TiN, Ta, TaN, W, WN, Re, Cr, Os, Mo and Ru taken individually or incombination.
 24. The component as claimed in claim 18, wherein thethickness of the copper-diffusion barrier layer is between 100 and 400Å.
 25. The component as claimed in claim 18, wherein the thickness ofthe turns is greater than 10 microns.
 26. The component as claimed inclaim 18, wherein the quality factor of the inductive microcomponent isgreater than 40 at 2 gigahertz.
 27. The component as claimed in claim18, wherein the resistivity of the turns is between 1.72 μΩ.cm and 1.82μΩ.cm.